The present invention relates to a process for the hydrolysis of ketoximes such as acetone oxime or methyl ethyl ketone oxime, and particular to the continuous acid hydrolysis of such ketoximes.
It has been proposed in U.S. Pat. No. 3,105,741 to Moore, Jr. et al. (1963) to produce concentrated acqueous solutions of hydroxylamine or hydroxylammonium salts from dilute aqueous solutions of such salts in a mixture with ammonium salts. A methyl ketone such as 2-octanone or 2-heptanone is reacted with the dilute solutions to form the corresponding oxime. The oxime is then phase separated in a countercurrent fashion from the dilute aqueous solution. The oxime is then hydrolyzed with relatively concentrated aqueous acid to reform the methyl ketone, which is then phase separated off leaving a concentrated salt solution. The methyl ketone is recycled to the oximation and the concentrated solution is evaporatively crystallized.
Japanese U.S. Pat. No. 7,102,413-R describes producing hydroxylammonium chloride of high purity by hydrolyzing methyl ethyl ketone oxime with aqueous hydrochloric acid of less than 20 weight percent HCl. The methyl ethyl ketone is distilled off, and the liquid then concentrated into crude crystals which are recrystallized with methanol. Other similar references are described in the background section of the Moore, Jr. et al. patent, with particular reference to U.S. Pat. No. 2,414,142 and the Journal of the American Chemistry Society, vol. 45, page 188 (1923).
While such processes are effective to produce concentrated hydroxylammonium salts from aqueous solutions via ketoximes, they require extensive amounts of equipment for serially oximating, phase separating, hydrolyzing and distilling off the ketone. Because of the apparently large reaction times required, substantial inventories, particular of ketone and ketoxime, would be required to practice the process.